This invention relates to a method of manufacturing a semiconductor device, and more specifically to a method of manufacturing a semiconductor device by forming a semiconductor thin film on a first substrate and transferring the thin film to a second substrate. The manufacturing method of this invention may for example be used to manufacture a composite semiconductor device by forming a light-emitting element array in the semiconductor thin film, affixing it to the second substrate and connecting other circuit elements.
An economical method of forming a light-emitting element is to form an intermediate layer on a sapphire substrate, form a compound semiconductor layer thereupon, and form a light-emitting part therein (Japanese Patent Kokai Publication No. H07-202265).
Also a method shown in FIG. 63A and FIG. 63B is known, in which the compound semiconductor is a GaAs semiconductor. In the method shown in FIG. 63, a sacrificial layer, i.e., a peeling layer (Al0.7Ga0.3As) 202 is formed between a GaAs substrate 201, and a GaAs thin film 203, as shown in FIG. 63A. The structure shown in FIG. 63A (GaAs/Al0.7Ga0.3As/GaAs) is immersed in hydrofluoric acid (HF) to separate the GaAs thin film 203, as shown in FIG. 63B).
In the aforesaid method, when the semiconductor thin film formed on the first substrate is peeled away (lifted off) from the whole surface of the substrate, it takes time for the etching solution used to etch the peeling layer to penetrate the peeling layer, so peeling (lifting-off) of the semiconductor thin film from the substrate is not easy. To resolve this problem, a possible solution is to divide the semiconductor thin film layer into pieces (small island regions formed, for example, by mesa etching) each of which will become a semiconductor device, and then etch the peeling layer underneath the semiconductor thin film.
Another problem arises when the semiconductor thin film may have a thickness of several μm or less, and in this case it is extremely difficult to handle the semiconductor thin film, for picking it up and bonding it to a second substrate. To eliminate the difficulty of handling the semiconductor thin films, individual support materials prepared on the semiconductor thin film pieces (island regions of the semiconductor thin film layer) may be provided to give a certain thickness and mechanical strength to the semiconductor thin film.
In the photolithography etching step to divide the semiconductor film into small island regions of semiconductor thin film layer, etching is performed using an etching mask which divides the semiconductor thin film layer into small island regions of semiconductor thin film layer. However, after dividing the semiconductor thin film into small island regions of the semiconductor thin film layer, and removing the etching mask, it is very difficult to provide a support material for handling each semiconductor thin film piece having exactly the same pattern as that of the semiconductor thin film piece; the pattern of the support material may be misaligned to that of the small island regions of the semiconductor thin film layer. When the support material does not cover completely the surface of the small island regions of the semiconductor thin film layer due to misalignment of the pattern of the support materials to the pattern of the small island regions of the semiconductor thin film layer, the edge region of the lifted-off semiconductor thin film pieces may easily break during handling of the lifted-off semiconductor thin film pieces. Also, if the support material pattern happens to cover the side edge regions of the sacrificial layer (the peeling layer) exposed to the air by the mesa etching grooves due to the patterning misalignment, it may be difficult, or even impossible to separate (lift off) the semiconductor thin film piece from the substrate.
On the other hand, if the peeling layer is etched over the whole of the substrate, the semiconductor thin film pieces on the substrate may become dissociated from each other. Also, after the peeling layer is etched over the whole of the substrate, it may be necessary to bond a plurality of (e.g., all) semiconductor thin film pieces to the second substrate all at once. In this case, handling the plurality of semiconductor thin film pieces is very difficult.